Studies will be continued on the mechanism of action of coenzyme A transferase with particular reference to the role of substrate specificity in providing the driving force for catalysis and the examination of model reactions. Work with model reactions will include the reaction of succinic acid thiol esters and the reactions of thiol esters with carboxylate anions. Studies on the formation of aminoquinones will be continued with the aim of elucidating the mechanism of the 1, 4 addition. The solvent isotope effect in enzyme catalysis will be studied at short times after mixing to obtain an evaluation of the importance of conformation changes. Rate accelerations in micelles will be examined with special reference to high order reactions that will show large favorable entropy contributions. The conformational changes of coenzyme A transferase will be followed by measurements of tritium exchange. The role of the sulfhydryl group in this enzyme will be evaluated. The mechanism of general acid catalysis of sulfhydryl anion addition to the carbonyl group will be studied. The mechanism of aminolysis of phenyl acetate catalyzed by general acids will be studied. BIBLIOGRAPHIC REFERENCES: H. White and W.P. Jencks. Mechanism and Specificity of Succinyl-CoA: 3-ketoacid Coenzyme A Transferase, J. Biol. Chem. 251, 1688-1699 (1976). H. White, F. Solomon and W.P. Jencks. Utilization of the Inactivation Rate of CoA Transferase by Thiol Reagents to Determine Properties of the Enzyme-CoA Intermediate, J. Biol. Chem. 251, 1700-1707 (1976).